Various types of penetrating bombs for attacking hardened targets are known. Penetrating bombs generally include a penetrator, a hard casing with an interior cavity for containing an explosive and a fuze to ignite the explosive. The bomb may include a guidance system to direct it to a target after release from an aircraft.
The ability of a penetrator to penetrate a target is proportional to the mass and the velocity of impact of the bomb and inversely proportional to the cross-sectional area of the bomb. In general, the greater the kinetic energy and the smaller the cross-sectional area, the greater the amount of penetration that can be expected. The cross-sectional area must, on the other hand, be sufficiently large to accommodate an internal cavity for carrying an explosive, and provide sufficient penetrator mass to withstand impact without breaking up so that penetration occurs.
Hardened targets, for example, below ground bunkers, have various features to defeat penetrating bombs. Typically, a hardened target includes layers of reinforced concrete, sand, earth, and rock, in various combinations and quantities to absorb or deflect the kinetic energy and explosive force energy of a penetrating bomb. In addition, voids or spaces may be provided between solid reinforcing layers, which allow an adjacent layer to collapse to absorb energy. Voids are also used to defeat fuzing systems that ignite the explosive when a void is sensed.
To overcome the increasingly sophisticated and effective protection features, ways of increasing the penetrating ability of the weapons have become needed. The present invention provides a solution by combining a rocket booster motor with a hard target penetrator in a structure that is compatible with current aircraft bomb carrying systems.
According to the invention, the bomb includes a penetrator formed as a hollow cylindrical body with a ogive shaped nose. The penetrator is formed from a tough, strong metallic alloy, and has a wall thickness sufficient to maintain structural integrity during penetration of a target so the penetrator will not buckle or collapse upon impact and penetration. The hollow interior contains an explosive or other payload and a fuze that initiates the explosive or other payload after the target has been penetrated. The penetrator may break into fragments from the force of the explosive or other payload, which adds to the effectiveness of the bomb.
According to a preferred embodiment of the invention, the rocket booster motor is configured as a wrap around unit, that is, an annular chamber that surrounds the penetrator. At least one exhaust nozzle, and preferably a plurality of nozzles, is positioned at an aft end of the rocket motor to provide propulsion. The wrap around rocket configuration results in a bomb with a penetrator having a practical length nearly equal to the bomb length, thus providing for an efficient penetrator size.
The invention also includes a guidance system for guiding the bomb after release from the aircraft, and for directing the bomb to the target.
According to a preferred embodiment of the invention, the guidance system includes an inertial navigation system (INS) with a global positioning system (GPS) that allows the guidance system to determine its location without assistance from the delivery aircraft. The guidance system uses vanes, that is, fins and wings, to control the flight of the bomb.
The guidance system according to the invention also includes accelerometers to sense accelerations experienced by the bomb for use in correcting the attitude of the bomb. Data from the accelerometers is used by the guidance system to control the wings or fins, or other control surfaces on the bomb.
According to the invention, the bomb includes a fuze for initiating the explosive or other payload after penetration of the target. The fuze can include, alternatively, a time delay or a layer sensing device for controlling when initiation occurs.